Lateral ankle sprains (LAS) and chronic ankle instability (CAI) are common musculoskeletal injuries that are a result of inversion injury during sport. The midfoot is frequently involved during inversion injury, is often overlooked during clinical examination, and maybe contributory to the development of CAI. The purpose of this study is to investigate multisegmented foot motion using a motion capture system, clinical joint physiological and accessory motion, and morphologic foot measurements in recreationally active men and women with and without a history of lateral ankle sprains and chronic ankle instability. Additionally, the effects of a joint mobilization intervention in patients with diminished multisegmented foot motion and intrinsic foot strengthening in healthy individuals will be investigated.

Arm 1:The purpose of this arm of the study is to determine if foot muscle exercises change the function of the foot. Up to 25 people will be enrolled in this arm of the study at the University of Virginia.

Arm 2: The purpose of this arm of the study is to determine if joint mobilization applied to the middle part of the foot will effect function in people who are healthy, have a history of lateral ankle sprains (LAS), or have chronic ankle instability (CAI) and have joint stiffness. Up to 125 people will be enrolled in this arm of the study at the University of Virginia. CAI is a condition where symptoms from an ankle sprain last longer than one year. These symptoms include a feeling of looseness, feelings that the participant may roll the ankle, or repeated ankle sprains. This study may help clinicians prescribe simple exercises at home to help treat CAI. The participants are being asked to be in this study, because they are physically active (participate in some form of physical activity for at least 20 minutes per day, three days per week) and are not currently seeking medical treatment/therapy for LAS/CAI. Joint mobilization is a commonly used clinical intervention used to decrease pain and increase joint range of motion. The home exercises employed for this study are commonly used clinically in the treatment of foot and ankle problems and include a foot and calf stretch and standing on one foot for 60 seconds. The participant will be asked to perform these exercises three times daily throughout the course of the day.

The investigators hypothesize that joint mobilization will improve patient oriented outcomes and measures of joint mobility and excursion in individuals with impaired foot mobility immediately post intervention and at 1-week follow-up, but not at 4 weeks; and intrinsic foot strengthening will result in differences in morphologic measures and intrinsic muscle cross-section in healthy individuals following a 4 week home exercise program.

Inclusion Criteria:

Healthy participants

• Aged 18-50
• All subjects will be physically active: Participating in some form of physical activity for at least 20 min per day, three times per week.
• All subjects will have no history of ankle injury.

LAS participants

• Aged 18-50
• All subjects with a history of ankle sprains, no lingering symptoms or disability, not actively receiving treatment for their ankle sprain
• All subjects will be physically active: Participating in some form of physical activity for at least 20 min per day, three times per week.

CAI participants

• Aged 18-50
• CAI with a history of recurrent ankle sprains, with the first sprain occurring longer than 12 months ago. They will have lingering symptoms, and disability, but not actively receiving treatment for their CAI
• All subjects will be physically active: Participating in some form of physical activity for at least 20 min per day, three times per week.

Exclusion Criteria:

• Neurological or vestibular disorders affecting balance
• Currently seeking medical care for LAS/CAI
• History of prior ankle surgery
• History of ankle or foot fracture
• Diabetes mellitus
• Current self-reported disability due to lower extremity pathology that may adversely affect neuromuscular function
• Lumbosacral radiculopathy
• Soft tissue disorders including Marfan's syndrome and Ehlers-Dandros syndrome
• Absolute contraindications to manual therapy
• Pregnancy